FOSSILS OF THE CLINTON GROUP. 117 



oblique to the body of the shell ; anterior end proportionally long and 

 full, faintly separated from the body of the shell by a very slightly 

 marked sulcus, which crosses the anterior .portion of the valves ; body of 

 the shell very full, almost inflated in the central part; the umbonal 

 region the most prominent, slightly angular for a short distance below 

 the apex, caused by an oblique flattening of the anterior side of the beak; 

 posterior slope concave between the postero- cardinal angle and the body 

 of the shell. Cardinal area and hinge characters unknown. 



Surface of the valves marked by very strong varices, or concentric un- 

 dulations of the surface, indicating stages of growth. 



The species is most nearly related to C. Sajfordi (=Pal8earca Saffordi, 

 Hall, 12th Kept. State Cab., p. 11 ; see, also, Pal. N. Y., Vol. III., p. 524; 

 =Cyrtodon Saffordi, Safford, Geol. Tennessee, p. 287, pi. F, fig. 2), but 

 differs in being more extended on the anterior end, in the greater 

 obliquity of the body of the shell, in the flattening or compression of the 

 anterior side of the beak, in the greater prominence of the umbonal 

 region, in the depression of the postero-cardinai slope, and in the faintly 

 marked sulcus crossing the anteiior portion of the valves. 



Formaiion and locdlity : In ihe iron ore beds of the Clinton group, at Wilmington, 

 Clinton county, Ohio. Ohio State collection. Collected by Prof. Edward Orton. 



GxlSTEROPODA. 



Genus PLEUROTOMARIA, DeFrance. 



Pleueotomapja inexpectans (n. sp.). 



Plate 5, fig. 12. 



Shell of medium size, very broadly conical above the middle of the 

 last volution, and abruptly rounded below. Spire moderately elevated? 

 the line of the opposite sides inclosing an angle of about eighty-five de- 

 grees, or a little less than a right angle. Volutions rather rapidh' in- 

 creasing in size, thickened, and slightly elevated at the upper margin, 

 forming a raised band just below the suture line, thence regularly sloping 

 to the periphery, which is obtusely angular. Lower side of the volution 

 very ventricose, and regularly rounded to the umbilical region, which is 

 filled by a small callus that appears to spread over and cover the colu- 

 mellar lip. Aperture forming more than one-third of the entire height of 

 the shell, regularly rounded, except above the center of the outer border, 

 where it is slightly flattened, corresponding to the upper sloping surface 



